Fender for dock wall



*April 21, 1970 Nuus/ao MIURA 3,507,123'- FENDER FOR` DOCK WALL FiledFeb. 20, 196B FIG. .1. FIG. 2;

LOO

MIS/ao MIURA Q @am @EFL Ec 7/0/v By United States Patent U.S. Cl. 61-482 Claims ABSTRACT OF THE DISCLOSURE A flexible hollow tubular fender fora dock wall is provided, having a base and a top buffer, and anintermediate resilient block which is ho-llow and has lateral sideswhich are each of a non-uniform cross-section.

The present invention relates to a fender to be fitted to a quay or dockwall for the purpose of absorbing the dynamic energy of a ship on beingmoored in a port `so that it can be safely moored without damaging thehull or the quay wall structure.

In recent years ships are becoming ever bigger. Particularly oil tankersor ore-carriers of 0,000-300,000 metric tons classes are being produced.With a tremendous kinetic energy p-resent in such giant vesels inmooring, a more effective cushioning device to protect the hull and themooring dock structure is now urgently in demand.

There are at present a variety of types of mooring fenders available forthis purpose, and most of them make use of the elasticity of rubber andcome in fairly large sizes. In their design, however, the major emphasisis laid on the absorption of the dynamic energy of mooring, and littleattention is paid to the possibility of hull damage or to the economy ofmooring structures. The fundamental requirement as to the fender is toabsorb as much impact energy as possible by a minimum reaction. Theexisting rubber fenders are found to be nearly satisfactory as far asthe ability of rubber elasticity to absorb the energy is concerned. Butthe existing r-ubber fenders are disadvantageous in that the better theycan absorb the energy, the larger the reaction they cause.

In the conventional design of such fenders, the contact area between therubber elements and the hull is small. This results in the developmentof a large compression stress in the contact area between the outsideplating of the hull and the fender, which causes hull damage and maylead to an accident. The compression stress developed on the part of thesurface of the hull in direct contact with the conventional fender isequal to about 60-150 metric tons per square meter, whereas the criticalloading Strength of the outside plating of the hull is about 30u40metric tons per square meter. Thus due to the application of a stressfar in excess of the allowed loading strength, the outside plating ofthe hull is often subjected to damage. The present practice now used asa countermeasure for this condition is to provide combined wooden boardsover the rubber fender to avoid direct contact of the outside plating ofthe hull with the rubber fender, or to provide driving -piles anderecting a concrete wall on the heads thereof.

,The magnitude of the reaction depends to a large extent on thesectional area of the members constituting the mooring structures. Thesmaller the reaction, the more economical will be the structurerequired.

Generally speaking, the structural designing of mooring facilities canmost reasonably be made in consideration of the magnitudes of themooring speeds and their frequency distribution. The mooring speed whichhas been taken as a design factor will not always be the one met inpractice, and a-ship will more often approach the quay at a considerablylower speed than that. It would be appropriate for designing to assumethe reaction due to a higher mooring speed of less frequency as ashort-term load, and provide acertain margin for the allowable stress ofstructural members for this load, while designing an allowable stressunder a long-term load for the reaction due to a lower mooring speed ofmore frequent occurrence. Such a designing method would give economicalsections of the structural'members, but the actual designing in practiceis influenced by the characteristics of a fender. For instance, take thecase of a circular fender in which the relation between the ymagnitudeof applied force of reaction and the involved strain gives a linearvariation. In such a fender there is a desirable tendency that theapplied force of reaction is small in the range of small energyabsorption and the force of reaction increases with an increase in theabsorbed energy. However, this type of fender has drawbacks in that thetotal energy absorption is too small and a firm fitting is difficult toattain.

In the case of a V-shaped fender, as heretofore used, the reaction risesto a certain extent in the initial stage, thereafter remaining constant4while the strain continues to grow; -accordingly there is noproportional relation betweenenergy absorption and reaction, and a largereaction occurs even in the range of small energy absorption. Such afender should be designed assuming an allowable stress under a long-termload for the section of structural member against a large reaction inthe initial stage. Thus, with an increased section required, theresulting structure will be less economical.

The ideal relation between the magnitude of reaction and energyabsorption would be represented in the initial operating stage by smallenergy absorption by the reaction of a circular fender, and in the lateroperating stage calling for large energy absorption by the reaction of aV-shaped fender.

The Ipresent invention has been developed in view of the above points.The following is a description of embodiments of the present invention,referring to the accompanying drawings, in which FIGURE l shows a sideelevation of a fender according to this present invention;

FIGURE 2 shows a side view of said fender;

FIGURE 3 shows an enlarged cross-section of FIG. 1 along the lineIII-III;

FIGURE 4 shows an enlarged section of FIG. 1 along the line IV-IV;

FIGURE 5 shows a comparison of characteristic curves to illustrate therelation between the load and the deflection against the fenders; and

FIGURE 6 shows a modified form of the fender in which outer faces of thefender are concave instead of fiat.

Referring to the drawings, the main body or principal part 1 of thefender is an approximately rectangular tube with an approximatelyelliptical bore 2 running longitudinally through its center and ispreferably of rubber or other resilient material. The base 3 of saidmain body or principal part 1 has a core plate 4 of iron or othermaterial embedded therein. It would be desirable to extend the base 3outside of the Wall of the main body so that said fender base may beeasy to fix to the `quay wall as by bolts 12. On the side of the fender,opposite to the base 3, there is a buffer member 5, in which is embeddeda core plate, preferably of metal, 8 and that is a grid-formconsolidation of longitudinal beams 6 and transverse beams 7 of iron andother material, with the top surfaces of said beams being exposed. Inthis embodiment, the transverse beams 7 are inserted to be higher thanthe longitudinal beams 6. In each of the spaces between adjacent pairsof transverse beams 7, there are arranged two pieces of wood 9, on oneedge of which notch or groove 9a are cut to receive the protruding edgesof longitudinal beams 6. The beams of core plate 8 to be embedded insaid buffer 5 are intended to prevent a deflection of core plate 8 andto distribute the applied load in that area. Therefore said pieces ofwood 9 may be covered with rubber. The side faces of the portion of thefender between the base 3 and the buifer 5, and the outside fender faceis flat and perpendicular to the base, and the inside surface thereof iswarped outward and provides a supporting structure 10, 10.

FIGURE 6 shows a modied form of the'fender in which the principal part 1is a substantially rectangular parallelopiped having a central bore 14with internal flat Walls 16 andv with two opposite outside faces 15which are concave symmetrically inward about a transverse axis midwaybetween the base and the buffer, and are substantially ofsemi-elliptical contour.

When the described fender structure is subjected to a ships impact, thisfender develops a deformation at first in its thinnest center portion 13of the supporting rubber structure, just as would be developed in acircular' fender, with the relation between the reaction and energyabsorption being similar to that in a circular fender.

When the applied strain in this condition rises to account for about 50%of the total strain, the force of reaction sharply increases, reaching acertain value; thereafter with hardly any increase in the force ofreaction, the strain alone increases, giving a large energy absorption.The later stage with this condition existing resembles the performanceof a V-shaped fender, as heretofore used. In FIGURE 5, which illustratesin characteristic curves the relation between the applied load and thedeflection against the fenders, curve A shows this relation for acircular fender, curve B shows the relation for a V-shaped fender asheretofore used, and curve C shows the relation for a novel fenderaccording to the present invention.

As described above, the fender of this present invention combines theperformances of both the known circular and the V-shaped fenders. Thatis, the reaction force vs. energy absorption relation of the fender ofthis present invention is that of a circular fender in the initial stagewith 0-50% applied strain and that of a V-shaped fender in the laterstage with 50-100% applied strain. The above mentioned characteristicswould be highly effective for economical designing of the mooringfacilities, because the low energy of mooring of frequent occurrencecould be absorbed in the initial stage of 0-5 0% applied strain; and thereaction force being small, an economical section could be obtained evenif designing structural members with an allowable stress under along-term load; meanwhile, the high energy of mooring of less frequencycould be absorbed in the later stage with 50-l00% strain. The reactionin this state would be larger than that in the initial stage, but onaccount of its less frequency it might be regarded as a short-term load.Accordingly, up to a 50% increase over the allowable stress under along-term load can be -permitted as a stress developed in the crosssection of the structural member of the fender.

Thus, adoption of a rubber fender of the design of this presentinvention will assure the construction of economical, highly safemooring structures which can protect vthe outside plating of the hullsurface from damage due to compression stress, and, with an idealrelation between y the constructions of the main body portion and thecore plate of the buffer being as described.

I claim:` 1. In a dock fender for absorbing the impact of a moor- A ingship, a principal part substantially of the shap`e of a rectangularparallelopiped and being provided with a central interior hollow space,a base at one end of said p'rincipal part formed integrally with saidprincipal part, a buffer portion at ythe opposite end of said principalpart formed integrally with said principal part, said principal part,said base and said buffer portion being formedof resilient material, thelateral portions of said principal part extending between said base andsaid buffer portion, having two inner opposite faces and two outeropposite faces and being of a non-uniform cross-section symmetricallyabout the plane midway between said base and said biiifer portion,either two opposite faces comprising respectively arcs of an ellipticalbore the long axis of which extends between said base and said bufferportion and the other two opposite faces being flat, and a reinforcingplate enbedded in said buffer portion.

2. A fender according to claim 1, wherein said reinforcing plate has anoutwardly projecting grid-form consolidation of longitudinal beams andtransverse beams, said grid-form consolidation being provided withprotecting members.

References Cited FOREIGN PATENTS 724,048 12/1965 Canada. 945,456 1/ 1964Great Britain. 1,098,276 1/ 1968 Great Britain.

JACOB SHAPIRO, Primary Examiner U.S. Cl. X.R. 114-219; 267--1

